Currently the centralized monitoring system of the large power computer room not only includes the main equipments, but also integrates power and environmental monitoring in one. In order to be compatible with more devices, such monitoring system adopts the popular Modbus communication protocol. But the common UPS only provides one RS232 interface, since it cannot connect to multiple devices and the communication protocol generally can’t satisfy multi-device trunk mode to be communicated according to IP address, thus such integrated monitoring device cannot be achieved. And then Modbus protocol conversion equipment is needed. Modbus card is intelligent protocol converter equipment, developed while adapting to the current market demand for power centralized monitoring applications.